No related application is known.
The present invention relates, in general, to optical communications and, more particularly, to a method to transmit information between entangled pairs of parametric down-converted photons.
It is clear that parametric down-converted signal and idler fields are incoherent and there is no observable interference in either the signal or idler fields separately. However the down-converted signal and idler fields do carry phase information about a coherent pump field through quantum entanglement. An earlier approach by Ou et al (reference: Z. Y. Ou, L. J. Wang, and L. Mandel, Phys. Rev. A 40, 1428, 1989) utilized a xe2x80x9ctwo-particlexe2x80x9d interferometer and a coincidence counter to show that, in coincidence, probability amplitudes for sibling signal and idler photons can provide a type of observable interference (fringing). This interference a result of the phase entanglement of the signal and idler photons with the down-converted photons in the coherent pump field.
The xe2x80x9ctwo-particlexe2x80x9d interferometer in the Ou et al experiment utilized probability amplitude wavefunction superposition and a coincidence counter to xe2x80x9csortxe2x80x9d both signal and idler photons. Our apparatus is a different xe2x80x9ctwo-particlexe2x80x9d interferometer, utilizing phase sorting xe2x80x9cpilot beamsxe2x80x9d which replace and remove the necessity of the coincidence counter in the Ou et al experiment, thereby observing interference from fringing without coincidence.
Fringing in the idler and signal beams, with this xe2x80x9cpilot beamxe2x80x9d provoked sorting, is observable because an xe2x80x9canti-fringingxe2x80x9d component is inhibited, thereby causing the xe2x80x9cfringingxe2x80x9d component to be observable. Normally the fringing and the anti-fringing components completely add and balance to remove any semblance of interference. The sorting from the coincidence counter in the original Ou et al interferomter acted to remove the anti-fringe component and in the apparatus described herein the xe2x80x9cpilot beamxe2x80x9d sorting likewise removes the anti-fringe component.
In the apparatus described herein observable interference in the signal field can be effected by changes in the idler or pilot fields. This is a gross non-local effect. Such a non-local effect could be exploited for advantages and/or advances in quantum computing and communications.
Communications between two spatially separated locations utilizing non-local entanglements of quantum particles, such as photons, has promise of being much faster than communications through other known means of transmission. The present invention provides the ability to communicate information, non-locally, between entangled signal and idler photons that are generate by a parametric down-conversion process.